The Study On The Hybrids Between Different Strains Of Bursaphelenchus Xylophilus And B.mucronatus

Bursaphelenchus xylophilus has caused great damage to the forestry and ecology system in some countries of North American and East Asia and Europe. It is difficult to control this disease if the forest is infected the pine wood nematode. Now many nematologists are studying B.xylophilus because it has been considered the dominant pathogen of pine wilt disease. B.mucronatus, a very close related species to the B.xylophilus whether in the life cycle, morphology or host plants, is get some attention from some nematologist.Inter-and intra-breeding were made between the 6 isolates from North American and Asia of Bursaphelenchus xylophilus and 8 isolates of B.mucronatus from Europe, Asia and North American in the laboratory conditions. Intra-breeding produced fertile offspring. Inter-breeding among B.xylophilus and B.mucronatus isolates produced offspring which mostly died out after one or several generations except the isolates of Fr2 us3, us3 Fr2.Fr2 us4 and R us4. There are some abnormal_nematodes in intra and inter-specific hybrids.The ITS region of Genomic DNA extracted from intra-and inter-breeding offspring were amplified by a set of primer and the PCR products were digested by several restriction edonucleases such as Alul, Msp. HaeIII, the results show that ITS-RFLP patterns of all intra-breeding and most inter-breeding are mixed patterns which contains typical fragments of their parents. The analysis of ITS-RFLP also demonstrates that genomic DNA of hybrids has components both from parents. Our experiments support the theory that B. xylophilus and B. mucronatus come from a common ancestor which was put forward by De Guiran.4-years black pine seedlings were inoculated with suspensions of B. xylophilus or B.mucronatus from North America, Asia and Europe or their intra- or interspecific hybrids. The results show that I: Most B.mucronatus isolates and their intraspecific hybrids has moderate or slight pathogenicity to 4 years black pine seedlings, the mortality rate is from 0 (Jpl isolate and RxJP1 isolate) to 62,5% (Fj2 isolate and Fr2xFj2 isolate) and the RHSindex is from 0 to 411(Fr2xFj2 isolate). II: 4 Inter-specific hybrids have moderate pathogenicity between their parents of B. mucronatus and B. xylophilus. the mortality rate is from 62.5% (Rxus4 isolate) to 82.5% (Fr2xUs3 isolate). RHS index, from 578 to 638,is almost no difference. III: The activity of cellulase in the secretion of B. xylophilus and B. mucronatus and their intra- or interspecific hybrids were also determined by DNS method. The results show that the celluiase activity of different isolates is from 3.33 (Fr2xUs3 isolate) to 7.99 (us3 isolate), The experiment demonstrates that there is no positive correlation between the pathogenicity of pine wood nematode and their cellulase activity.